I have read previous posts that describe God’s promise to bring us back when we have strayed. I have a close friend who has openly rebelled against God after claiming to be saved, even pointing out to anyone who will listen the places where he says the Bible is wrong. If attempting to destroy the faith of others and leading lost souls to destruction is his goal, how can God exist in this man? Is it possible in extreme situations to lose God completely?
No one can accurately determine the spiritual condition of another person. Even such extreme behavior as you describe is not conclusive. But there are only two alternatives. People are either forever saved or they were never saved. Either way, you should pray for your friend while there’s still time for him to get into a right relationship with God.
You may not know what’s in your friend’s heart but the Lord does, and it’s His desire that none should perish but that all would come to repentance (2 Peter 3:9). Therefore your prayers for him are in alignment with God’s desire.
As for losing God, that’s not ours to do. God has purchased us (1 Cor. 6:20), set His seal of ownership on us, and put His Spirit in our hearts as a guarantee of our destiny with Him (2 Cor. 1:21-22). And Jesus promised not to lose any of those the Father has given Him (John 6:38-40). The entire Trinity is pledged to our security and there’s no power in Heaven or on Earth strong enough to ever change that.
“For no matter how many promises God has made, they are “Yes” in Christ. And so through Him the “Amen” is spoken by us to the glory of God” (2 Cor. 1:20).